The courthouse and jail were designated as National Historic Landmarks by the U.S. Department of the Interior in 1973.

As part of the internal improvements campaign carried out by the South Carolina Board of Public Works in the 1820s, Robert Mills designed at least fourteen courthouses and fourteen jails throughout the state. The Lancaster County courthouse and jail are among the best surviving examples of his work from this period. Set on a raised basement, the two-story brick courthouse is characterized by Palladian symmetry and features a pedimented portico with modified Tuscan columns. A double flight of steps leads to an entrance with a semicircular fanlight set in a molded pediment. The vaulted ground story has solid brick walls no less than two feet thick; those on the second story measure eighteen inches. The courtroom, located on the second floor, is finished with wainscoting and reeded woodwork. The courthouse has remained in use since its construction. Its elegant styling makes it one of the most refined examples of Mills’s early public buildings.

The jail, located one block from the courthouse, is a two-story stuccoed masonry building with few exterior features. Its design incorporates several innovations advocated by Mills. Barred cells are situated in the center of the prison rooms to facilitate circulation, which Mills believed necessary for inmates’ health. Prisoners were also arranged according to their crimes: debtors on the first floor and others above. The austere exterior of the building features stone quoins and belt courses and recessed arches on the ground floor. County officials decided to discontinue use of the building as a jail after a cell-block fire caused the deaths of eleven inmates in December 1979. Today it is an office building. The courthouse and jail were designated as National Historic Landmarks by the U.S. Department of the Interior in 1973.